New member, New Princeton Reverb build, weak Tremolo/Reverb!

[sjcasas]

Hi all!
So, this build started as an EBay chassis, bought most of the parts from Hoffman, made the cabinet myself (Cherry/curly Maple), Warehouse G12C/S Speaker... anyways...


Checked, double checked, brought it up on the Variac, checking with three multimeters simultaniously, everything looked good. Played it for a bit through a HUGE 250W speaker because the GS12C/S wasn't here yet. Sounded ok, a bit harsh (maybe), trem didn't work (very faint) and the reverb wasn't hooked up yet, traded some tubes out, left it on for a few hours while I cleaned up the shop, checking on it from time to time. No smells, no heat issues, pointed a laser thermometer all over it looking for heat. All looked good. Reverb cables came the next day, so I fired up the reverb and it is VERY WEAK! It's there, just barely.
So I read up on the forum and found some others with this issue and read up on many possible fixes. Oh yeah, I did start out with a 12AT7 in V2. I have NOT tried to swap it w/ a 12AX7 yet.


Anyways, I will try some of the fixes mentioned in Sluckey's post "Is your tremolo too weak?" tonight. I just wanted to post some pictures and hear about any other fixes that might have come up since 2013!

[sjcasas]

More Pics...

[sjcasas]

Still more pics...

[sjcasas]

One more pic... the most important of all...

[sluckey]

A stock PR should have a strong reverb and tremolo. Is yours stock or is it juiced up?

[sjcasas]

No... stock Hoffman layout. Not one change except for carbon Comp mojo, and a few capacitor type changes... all values are stock.

[sluckey]

Pin 2 voltages for V1, V3, and V4 are very wrong.

[2deaf]

Does the vibrato have 0.1uF instead of 0.01uF capacitors?

[sjcasas]

Good call, 2deaf... so much for my double-check...
I'm triple-checking right now... gotta find out about those wrong voltages...

[sjcasas]

Sorry Sluckey... it's supposed to say pin 1 and pin 6...

[sjcasas]

How's this?


Oh, and if I remember correctly, I can make a shorting plug to insert into the Vibrato switch jack to turn it off, right? Because, yeah... it's working now... heh.

[sjcasas]

Wow! This thing sounds AWESOME! Just like my Deluxe Reverb... Speaker is brand new so will break in eventually. Tremolo ticks. Need to make a back, add standby switch, maybe plug the ext. speaker hole, better faceplate/backplate, and choose a grill cloth.
Gonna play it with the band this Sunday. I'm sure it will be a bit underpowered and I will want to soup it up at that point. My goal is to get it up to about 22W like my DR. Pretty sure I will need new iron and a phase inverter re-arrangement. What I want is basically a Deluxe Reverb in a smaller, single channel package. So, probably the single channel, no trem kit is next!
Also, I got some bad info on the net about the angle of the front of the chassis and built this amazing Cherry/Maple cabinet WRONG! So, now I will build a tolex'd cab for this one, and get some repro faceplates and maybe SELL IT.
I'll post some sound clips tomorrow.

[sjcasas]

Ok, I played with the band the other night and I had to turn it up past the sweet spot for me. Too crunchy, I need a bit more headroom and cleaner.  Otherwise, it was AWESOME. Sounded and felt like my Deluxe Reverb with my TS9 on mild. But for sure it just wouldn't do with my other drummer. I'd have to mic it.


So I'm thinking about the Stokes mod. Can anyone confirm that this is indeed all I have to do?

[sluckey]

I don't know if you'll be able to rise above a moderate drummer without mic. I had one back in the '60s. No way could it keep up with a C&W band. Forget about R&R. No one was micing amps back then either.

[sjcasas]

Well, maybe it was the 12" speaker and the small room, but it ALMOST did the other night. Almost, and If I could just get a bit more clean headroom, I feel like it might.


So, was that about the gist of the Stokes Mod for the Hoffman Layout?

[sluckey]

My comments were about the PR in general. I see the stokes mod just uses a higher B+ node for the PI? Looks simple enough to try. Maybe take you a couple minutes to know if it will get you enough headroom.

[alerich]

The Stokes mod helps in these situations. I do a modified Stokes mod. I pick up the PI and the stage before it and connect both of them to the unused power supply node. I also add another 22uf filter capacitor across the first node to beef it up a bit. The 5AR4 can handle it fine. There's a definite audible difference with then mods but I only play at home. Whether it will be enough for your situation (I'm skeptical) you'll have to try it to find out.

[MFowler]

There are so many mods for the PR it's kind of pick and choose.


Paul C. mod
Richie Hall mod
Tim Marcus-Milkman Amps mod
David Allen-Allen Amps mod
Billy Z. mod


Mark

[SILVERGUN]

Need to make a back

I've experimented with this size cab with the back on and off and I feel that it sounds more full (better) with no back panel. I made one for a local guy(who plays out in a Beatles tribute band) and he agrees, and plays it with the back panels off. His drummer says he can hear him better that way.
Also, the speaker you chose is specifically designed to tame high end and that might mask some of the clarity you need to get over a drummer.
I would not hesitate to try a different speaker.
My friend is doing it with a Warehouse ET-90, and he is one of those flakey, tone obsessed, gear heads.
It looks like Warehouse speakers have finally gone up in price so I'm not sure I can still justify them.

[shooter]

he is one of those flakey, tone obsessed, gear heads.

those are the best kind for learning to translate electronics to music 

[Ed_Chambley]

I am not an obsessed great head flake, but I use a AA1164 sort of.  I used enough MA to run 5881 and used a Deluxe OT.  The voltages are about 20% higher than stock.  I reduced the bypass cap value of v1 to 4.7uf.  If you get some of the Bass out of the circuit prior, you wattage will reflect more of the guitar signal.


Normally 6v6 work just fine, but I must reveal I use another amp too.  Both are about 15 watts now.  Ac15 and it is closed back and has a 12.



Not guaranteed 4.7uf, but memory says.  I just kept pushing it until it worked.



There are a lot of Princeton mods.  I run 2, 10 and have no problem playing over a drummer or said another way, I have no problem being heard over a drummer I would gig a Princeton with.  I have few 30, 50, and 100 watt amps and some very efficent speakers if the need arises which happens only outside these days.


Truthfully, with this no backline stage we are seeing a lot of these days, it is good to have a small amp.

[sjcasas]

Alerich: I did the Stokes and the Sweet Pot. I use pedals. I haven't had the chance to test it with the band because everyone keeps acting like their wives and kids and careers are more important than jamming with the boys.    I'll report back when I do. In the meantime, just gonna leave this here: https://www.youtube.com/watch?v=0IU1kQ1Mfsk
Discuss...


MFowler: Thanks, I will read up on ALL of those!


Silvergun: So far I really like the speaker. It's def not broken in yet and I have hearing issues, but my keyboard player is a tech and one of those guys that wears hearing protection whilst jamming (sisssy... )  and he says it's GREAT. A huge improvement.  Besides, the absolute BEST part about this speaker is that it is ORANGE! Oh yeah, I wasn't talking about closing the back off, just making a back panel like Fender did. I also prefer open backs.


Ed Chambley: I will try changing that cap next. Easy enough, but I really want to keep any low freq definition I have.
My friend has a beat up Tweed Deluxe that he somehow crammed a 15" speaker in. He swears it is as loud as his 50w Plexi, dialed in for equivalent headroom and such... Maybe he means that is is loud enough that he can use either for same gig in most small/medium rooms.

Anyway, I think I am most interested in getting THIS amp to be enough so that STAGE VOLUME, on the CLEAN side with headroom, for MY own monitoring purposes, with MY hearing issues (mild tinnitus/loss), can be used for gigging with mics used when needed for FOH. And I'm starting to suspect that I ought to just spring for DR PT and OT and added choke next.

Thanks for all the help. I hope to have a jam this weekend and I will report back.

[sjcasas]

Oh yeah... I forgot to mention that I have a solid state plug-in recto that I will try next time we jam in the hopes that it increases my clean headroom and firms up the bass. I don't like flabby bottom end. Know what I'm sayin? Know what I'm sayin?  Probably give me some volume, too. Also, I added a standby switch in the ground sw hole because you never know when 'taking 5' will turn into 'taking 45' and I like it to stay warmed up and ready. Besides, I think the solid state recto might slam the tubes if they are cold. Maybe I'm wrong about that...


The 'sweet pot' is just because I read (Robinette?) that when using pedal and humbuckers you may experience blocking distortion with this circuit. I use a clean boost and TWO TS-9's, among other things, and mostly single-coil guitars, but I like to have the option. I put it in the Ext Spk hole.


And I have to post this smiley... just because...
 

[sjcasas]

I just realized that I never "reported back" about this amp and the mods. I hate when people don't do that. Sorry.
This amp has lived with the SS recto ever since. It is pretty tight in the bottom end, and almost loud enough for small gigs. Jazz for sure, and maybe slow blues gigs. For anything other than that it needs to be mic'd. It still is a bit harsh for my tastes. I played a few gigs with it along with my Deluxe Reverb, both mic'd, and it was nice having the tighter bottom and mids of the Princeton clone. My Deluxe is a bit dark, warm, and creamy, I guess. These two pair really well. I really think that a speaker change would do this Princeton clone justice... maybe a Weber Jensen clone?
Anyways, it is my daughters, now, and, although I hope she becomes a touring musician at some point, she will probably play it in her living room from now on. And it just sounds GREAT! I am currently building another one for my other daughter and it will have a Weber 12F150. And also, I now have all the parts to build another one FOR ME! This time with a Celestion Vintage 30.

I am VERY happy with the Hoffman circuit. It is very well thought out and the turret board is a pleasure to work with. I've been re-building amps and modding them for years but this was my first scratch build and I am grateful Hoffman made it so painless. Also, kudos to Rob Robinette for his awesome website full of info!